Well, I took an extra rest day before W4R1 to give my knees an extra day's rest. Set off (wearing my new trainers) and it was okay but my knees were sore again later. So, I took 2 rest days before doing W4R2 - today. Knees were sore during the session. So frustrating as I felt like I had the stamina to run better / further / faster but my knees were having none of it - especially the right one. I completed the session (running on grass) but VERY slowly and cautiously. Did some good stretch exercises afterwards and am now elevating my knees and using an ice pack (although they don't look swollen). I plan to continue to take an extra rest day if my knees need it and to keep going with the programme and see if it's just 'beginner's knee' and also see if the new trainers help. I'll seek a medical view if it doesn't become easier soon.